Section 112(f)(2)(A) of the 1990 Clean Air Act Amendments (CAA) requires EPA to evaluate whether emission standards that were previously adopted under the technology-based, Maximum Achievable Control Technology (MACT) program provide an ample margin of safety to protect public health and prevent adverse environmental effects (taking into consideration costs, energy, safety, and other relevant factors). Within 8 years of the promulgation of a MACT standard for the source category, EPA is mandated by the CAA to assess the risks to determine whether additional standards are needed. If additional risk reductions are necessary to protect public health with an ample margin of safety or to prevent adverse environmental effects, EPA must develop standards to address these remaining risks. Because the risk review is an important component of the Risk and Technology Reviews (RTR) process, the EPA is seeking SAB input on the scientific credibility of specific enhancements made to the agency's risk assessment methodologies, particularly with respect to screening methodologies, since the last SAB review was completed in 2010.